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Re: Hold Downs With No Plywood Ductility

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How long had the assembly been in place before the testing was done. 2 weeks or 20 years? Not that this is definitely the case, but it would seem that the frictional interface between the plywood and the studs would add significantly to the stiffness of the assembly until the studs and sheathing reduced in size due to moisture-loss related shrinkage. Maybe they should test some assemblies after running them a few months in a kiln?

Of course, that would require a 2-5 year waiting period from the time of construction to time of safe occupancy. That might not sit well with the NAHB. ;-)

Jordan



David Merrick, SE wrote:
Just heard a rumor out of San Jose State University.

The ASD Hold Down capacity was 30% higher than the Plywood shear wall and yet the Hold Down failed by ripping the screws out of the stud. The plywood showed no obvious signs of distortion relative to the studs. So the wall must have lifted off the base still square in shape.

Ultimate load was 4.7 times the sheathing design capacity and 3.5 times the holdown capacity.

Something is seriously wrong. This is the second event I have heard of where the HD failed before the plywood.

Ultimate strength of plywood needs to be reconsidered to not first fail the HD, Resulting in little plywood ductility. You know, the stuff that allows the very high rho of 6.5

David Merrick, SE

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